769 lines
21 KiB
C
769 lines
21 KiB
C
/*
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* Copyright (c) 2001 Jake Burkholder <jake@FreeBSD.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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/***
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Here is the logic..
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If there are N processors, then there are at most N KSEs (kernel
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schedulable entities) working to process threads that belong to a
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KSEGROUP (kg). If there are X of these KSEs actually running at the
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moment in question, then there are at most M (N-X) of these KSEs on
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the run queue, as running KSEs are not on the queue.
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Runnable threads are queued off the KSEGROUP in priority order.
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If there are M or more threads runnable, the top M threads
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(by priority) are 'preassigned' to the M KSEs not running. The KSEs take
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their priority from those threads and are put on the run queue.
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The last thread that had a priority high enough to have a KSE associated
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with it, AND IS ON THE RUN QUEUE is pointed to by
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kg->kg_last_assigned. If no threads queued off the KSEGROUP have KSEs
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assigned as all the available KSEs are activly running, or because there
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are no threads queued, that pointer is NULL.
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When a KSE is removed from the run queue to become runnable, we know
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it was associated with the highest priority thread in the queue (at the head
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of the queue). If it is also the last assigned we know M was 1 and must
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now be 0. Since the thread is no longer queued that pointer must be
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removed from it. Since we know there were no more KSEs available,
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(M was 1 and is now 0) and since we are not FREEING our KSE
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but using it, we know there are STILL no more KSEs available, we can prove
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that the next thread in the ksegrp list will not have a KSE to assign to
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it, so we can show that the pointer must be made 'invalid' (NULL).
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The pointer exists so that when a new thread is made runnable, it can
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have its priority compared with the last assigned thread to see if
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it should 'steal' its KSE or not.. i.e. is it 'earlier'
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on the list than that thread or later.. If it's earlier, then the KSE is
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removed from the last assigned (which is now not assigned a KSE)
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and reassigned to the new thread, which is placed earlier in the list.
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The pointer is then backed up to the previous thread (which may or may not
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be the new thread).
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When a thread sleeps or is removed, the KSE becomes available and if there
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are queued threads that are not assigned KSEs, the highest priority one of
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them is assigned the KSE, which is then placed back on the run queue at
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the approipriate place, and the kg->kg_last_assigned pointer is adjusted down
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to point to it.
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The following diagram shows 2 KSEs and 3 threads from a single process.
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RUNQ: --->KSE---KSE--... (KSEs queued at priorities from threads)
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\ \____
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\ \
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KSEGROUP---thread--thread--thread (queued in priority order)
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\ /
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\_______________/
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(last_assigned)
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The result of this scheme is that the M available KSEs are always
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queued at the priorities they have inherrited from the M highest priority
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threads for that KSEGROUP. If this situation changes, the KSEs are
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reassigned to keep this true.
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***/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include "opt_sched.h"
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/kdb.h>
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#include <sys/kernel.h>
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#include <sys/ktr.h>
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#include <sys/lock.h>
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#include <sys/mutex.h>
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#include <sys/proc.h>
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#include <sys/queue.h>
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#include <sys/sched.h>
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#if defined(SMP) && (defined(__i386__) || defined(__amd64__))
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#include <sys/smp.h>
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#endif
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#include <machine/critical.h>
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#if defined(SMP) && defined(SCHED_4BSD)
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#include <sys/sysctl.h>
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#endif
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#ifdef FULL_PREEMPTION
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#ifndef PREEMPTION
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#error "The FULL_PREEMPTION option requires the PREEMPTION option"
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#endif
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#endif
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CTASSERT((RQB_BPW * RQB_LEN) == RQ_NQS);
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/************************************************************************
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* Functions that manipulate runnability from a thread perspective. *
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************************************************************************/
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/*
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* Select the KSE that will be run next. From that find the thread, and
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* remove it from the KSEGRP's run queue. If there is thread clustering,
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* this will be what does it.
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*/
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struct thread *
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choosethread(void)
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{
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struct kse *ke;
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struct thread *td;
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struct ksegrp *kg;
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#if defined(SMP) && (defined(__i386__) || defined(__amd64__))
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if (smp_active == 0 && PCPU_GET(cpuid) != 0) {
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/* Shutting down, run idlethread on AP's */
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td = PCPU_GET(idlethread);
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ke = td->td_kse;
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CTR1(KTR_RUNQ, "choosethread: td=%p (idle)", td);
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ke->ke_flags |= KEF_DIDRUN;
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TD_SET_RUNNING(td);
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return (td);
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}
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#endif
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retry:
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ke = sched_choose();
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if (ke) {
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td = ke->ke_thread;
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KASSERT((td->td_kse == ke), ("kse/thread mismatch"));
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kg = ke->ke_ksegrp;
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if (td->td_proc->p_flag & P_SA) {
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if (kg->kg_last_assigned == td) {
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kg->kg_last_assigned = TAILQ_PREV(td,
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threadqueue, td_runq);
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}
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TAILQ_REMOVE(&kg->kg_runq, td, td_runq);
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kg->kg_runnable--;
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}
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CTR2(KTR_RUNQ, "choosethread: td=%p pri=%d",
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td, td->td_priority);
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} else {
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/* Simulate runq_choose() having returned the idle thread */
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td = PCPU_GET(idlethread);
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ke = td->td_kse;
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CTR1(KTR_RUNQ, "choosethread: td=%p (idle)", td);
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}
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ke->ke_flags |= KEF_DIDRUN;
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/*
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* If we are in panic, only allow system threads,
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* plus the one we are running in, to be run.
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*/
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if (panicstr && ((td->td_proc->p_flag & P_SYSTEM) == 0 &&
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(td->td_flags & TDF_INPANIC) == 0)) {
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/* note that it is no longer on the run queue */
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TD_SET_CAN_RUN(td);
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goto retry;
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}
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TD_SET_RUNNING(td);
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return (td);
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}
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/*
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* Given a surplus KSE, either assign a new runable thread to it
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* (and put it in the run queue) or put it in the ksegrp's idle KSE list.
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* Assumes that the original thread is not runnable.
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*/
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void
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kse_reassign(struct kse *ke)
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{
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struct ksegrp *kg;
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struct thread *td;
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struct thread *original;
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mtx_assert(&sched_lock, MA_OWNED);
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original = ke->ke_thread;
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KASSERT(original == NULL || TD_IS_INHIBITED(original),
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("reassigning KSE with runnable thread"));
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kg = ke->ke_ksegrp;
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if (original)
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original->td_kse = NULL;
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/*
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* Find the first unassigned thread
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*/
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if ((td = kg->kg_last_assigned) != NULL)
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td = TAILQ_NEXT(td, td_runq);
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else
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td = TAILQ_FIRST(&kg->kg_runq);
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/*
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* If we found one, assign it the kse, otherwise idle the kse.
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*/
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if (td) {
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kg->kg_last_assigned = td;
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td->td_kse = ke;
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ke->ke_thread = td;
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CTR2(KTR_RUNQ, "kse_reassign: ke%p -> td%p", ke, td);
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sched_add(td, SRQ_BORING);
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return;
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}
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ke->ke_state = KES_IDLE;
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ke->ke_thread = NULL;
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TAILQ_INSERT_TAIL(&kg->kg_iq, ke, ke_kgrlist);
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kg->kg_idle_kses++;
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CTR1(KTR_RUNQ, "kse_reassign: ke%p on idle queue", ke);
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return;
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}
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#if 0
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/*
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* Remove a thread from its KSEGRP's run queue.
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* This in turn may remove it from a KSE if it was already assigned
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* to one, possibly causing a new thread to be assigned to the KSE
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* and the KSE getting a new priority.
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*/
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static void
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remrunqueue(struct thread *td)
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{
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struct thread *td2, *td3;
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struct ksegrp *kg;
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struct kse *ke;
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mtx_assert(&sched_lock, MA_OWNED);
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KASSERT((TD_ON_RUNQ(td)), ("remrunqueue: Bad state on run queue"));
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kg = td->td_ksegrp;
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ke = td->td_kse;
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CTR1(KTR_RUNQ, "remrunqueue: td%p", td);
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TD_SET_CAN_RUN(td);
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/*
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* If it is not a threaded process, take the shortcut.
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*/
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if ((td->td_proc->p_flag & P_SA) == 0) {
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/* Bring its kse with it, leave the thread attached */
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sched_rem(td);
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ke->ke_state = KES_THREAD;
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return;
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}
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td3 = TAILQ_PREV(td, threadqueue, td_runq);
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TAILQ_REMOVE(&kg->kg_runq, td, td_runq);
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kg->kg_runnable--;
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if (ke) {
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/*
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* This thread has been assigned to a KSE.
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* We need to dissociate it and try assign the
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* KSE to the next available thread. Then, we should
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* see if we need to move the KSE in the run queues.
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*/
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sched_rem(td);
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ke->ke_state = KES_THREAD;
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td2 = kg->kg_last_assigned;
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KASSERT((td2 != NULL), ("last assigned has wrong value"));
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if (td2 == td)
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kg->kg_last_assigned = td3;
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kse_reassign(ke);
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}
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}
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#endif
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/*
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* Change the priority of a thread that is on the run queue.
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*/
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void
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adjustrunqueue( struct thread *td, int newpri)
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{
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struct ksegrp *kg;
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struct kse *ke;
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mtx_assert(&sched_lock, MA_OWNED);
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KASSERT((TD_ON_RUNQ(td)), ("adjustrunqueue: Bad state on run queue"));
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ke = td->td_kse;
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CTR1(KTR_RUNQ, "adjustrunqueue: td%p", td);
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/*
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* If it is not a threaded process, take the shortcut.
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*/
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if ((td->td_proc->p_flag & P_SA) == 0) {
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/* We only care about the kse in the run queue. */
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td->td_priority = newpri;
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if (ke->ke_rqindex != (newpri / RQ_PPQ)) {
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sched_rem(td);
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sched_add(td, SRQ_BORING);
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}
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return;
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}
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/* It is a threaded process */
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kg = td->td_ksegrp;
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TD_SET_CAN_RUN(td);
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if (ke) {
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if (kg->kg_last_assigned == td) {
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kg->kg_last_assigned =
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TAILQ_PREV(td, threadqueue, td_runq);
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}
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sched_rem(td);
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}
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TAILQ_REMOVE(&kg->kg_runq, td, td_runq);
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kg->kg_runnable--;
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td->td_priority = newpri;
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setrunqueue(td, SRQ_BORING);
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}
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void
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setrunqueue(struct thread *td, int flags)
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{
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struct kse *ke;
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struct ksegrp *kg;
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struct thread *td2;
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struct thread *tda;
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int count;
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CTR4(KTR_RUNQ, "setrunqueue: td:%p ke:%p kg:%p pid:%d",
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td, td->td_kse, td->td_ksegrp, td->td_proc->p_pid);
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mtx_assert(&sched_lock, MA_OWNED);
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KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)),
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("setrunqueue: bad thread state"));
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TD_SET_RUNQ(td);
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kg = td->td_ksegrp;
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if ((td->td_proc->p_flag & P_SA) == 0) {
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/*
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* Common path optimisation: Only one of everything
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* and the KSE is always already attached.
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* Totally ignore the ksegrp run queue.
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*/
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sched_add(td, flags);
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return;
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}
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tda = kg->kg_last_assigned;
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if ((ke = td->td_kse) == NULL) {
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if (kg->kg_idle_kses) {
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/*
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* There is a free one so it's ours for the asking..
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*/
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ke = TAILQ_FIRST(&kg->kg_iq);
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CTR2(KTR_RUNQ, "setrunqueue: kg:%p: Use free ke:%p",
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kg, ke);
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TAILQ_REMOVE(&kg->kg_iq, ke, ke_kgrlist);
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ke->ke_state = KES_THREAD;
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kg->kg_idle_kses--;
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} else if (tda && (tda->td_priority > td->td_priority)) {
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/*
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* None free, but there is one we can commandeer.
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*/
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ke = tda->td_kse;
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CTR3(KTR_RUNQ,
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"setrunqueue: kg:%p: take ke:%p from td: %p",
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kg, ke, tda);
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sched_rem(tda);
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tda->td_kse = NULL;
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ke->ke_thread = NULL;
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tda = kg->kg_last_assigned =
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TAILQ_PREV(tda, threadqueue, td_runq);
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}
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} else {
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/*
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* Temporarily disassociate so it looks like the other cases.
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*/
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ke->ke_thread = NULL;
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td->td_kse = NULL;
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}
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/*
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* Add the thread to the ksegrp's run queue at
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* the appropriate place.
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*/
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count = 0;
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TAILQ_FOREACH(td2, &kg->kg_runq, td_runq) {
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if (td2->td_priority > td->td_priority) {
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kg->kg_runnable++;
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TAILQ_INSERT_BEFORE(td2, td, td_runq);
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break;
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}
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/* XXX Debugging hack */
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if (++count > 10000) {
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printf("setrunqueue(): corrupt kq_runq, td= %p\n", td);
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panic("deadlock in setrunqueue");
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}
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}
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if (td2 == NULL) {
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/* We ran off the end of the TAILQ or it was empty. */
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kg->kg_runnable++;
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TAILQ_INSERT_TAIL(&kg->kg_runq, td, td_runq);
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}
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/*
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* If we have a ke to use, then put it on the run queue and
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* If needed, readjust the last_assigned pointer.
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*/
|
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if (ke) {
|
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if (tda == NULL) {
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/*
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* No pre-existing last assigned so whoever is first
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* gets the KSE we brought in.. (maybe us)
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*/
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td2 = TAILQ_FIRST(&kg->kg_runq);
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KASSERT((td2->td_kse == NULL),
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("unexpected ke present"));
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td2->td_kse = ke;
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ke->ke_thread = td2;
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kg->kg_last_assigned = td2;
|
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} else if (tda->td_priority > td->td_priority) {
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/*
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* It's ours, grab it, but last_assigned is past us
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* so don't change it.
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*/
|
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td->td_kse = ke;
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ke->ke_thread = td;
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} else {
|
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/*
|
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* We are past last_assigned, so
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* put the new kse on whatever is next,
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* which may or may not be us.
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*/
|
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td2 = TAILQ_NEXT(tda, td_runq);
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kg->kg_last_assigned = td2;
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td2->td_kse = ke;
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ke->ke_thread = td2;
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}
|
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sched_add(ke->ke_thread, flags);
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} else {
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CTR3(KTR_RUNQ, "setrunqueue: held: td%p kg%p pid%d",
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td, td->td_ksegrp, td->td_proc->p_pid);
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}
|
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}
|
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|
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/*
|
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* Kernel thread preemption implementation. Critical sections mark
|
|
* regions of code in which preemptions are not allowed.
|
|
*/
|
|
void
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critical_enter(void)
|
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{
|
|
struct thread *td;
|
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|
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td = curthread;
|
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if (td->td_critnest == 0)
|
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cpu_critical_enter(td);
|
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td->td_critnest++;
|
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}
|
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|
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void
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critical_exit(void)
|
|
{
|
|
struct thread *td;
|
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|
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td = curthread;
|
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KASSERT(td->td_critnest != 0,
|
|
("critical_exit: td_critnest == 0"));
|
|
if (td->td_critnest == 1) {
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#ifdef PREEMPTION
|
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mtx_assert(&sched_lock, MA_NOTOWNED);
|
|
if (td->td_pflags & TDP_OWEPREEMPT) {
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mtx_lock_spin(&sched_lock);
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mi_switch(SW_INVOL, NULL);
|
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mtx_unlock_spin(&sched_lock);
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}
|
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#endif
|
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td->td_critnest = 0;
|
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cpu_critical_exit(td);
|
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} else {
|
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td->td_critnest--;
|
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}
|
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}
|
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|
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/*
|
|
* This function is called when a thread is about to be put on run queue
|
|
* because it has been made runnable or its priority has been adjusted. It
|
|
* determines if the new thread should be immediately preempted to. If so,
|
|
* it switches to it and eventually returns true. If not, it returns false
|
|
* so that the caller may place the thread on an appropriate run queue.
|
|
*/
|
|
int
|
|
maybe_preempt(struct thread *td)
|
|
{
|
|
#ifdef PREEMPTION
|
|
struct thread *ctd;
|
|
int cpri, pri;
|
|
#endif
|
|
|
|
mtx_assert(&sched_lock, MA_OWNED);
|
|
#ifdef PREEMPTION
|
|
/*
|
|
* The new thread should not preempt the current thread if any of the
|
|
* following conditions are true:
|
|
*
|
|
* - The current thread has a higher (numerically lower) or
|
|
* equivalent priority. Note that this prevents curthread from
|
|
* trying to preempt to itself.
|
|
* - It is too early in the boot for context switches (cold is set).
|
|
* - The current thread has an inhibitor set or is in the process of
|
|
* exiting. In this case, the current thread is about to switch
|
|
* out anyways, so there's no point in preempting. If we did,
|
|
* the current thread would not be properly resumed as well, so
|
|
* just avoid that whole landmine.
|
|
* - If the new thread's priority is not a realtime priority and
|
|
* the current thread's priority is not an idle priority and
|
|
* FULL_PREEMPTION is disabled.
|
|
*
|
|
* If all of these conditions are false, but the current thread is in
|
|
* a nested critical section, then we have to defer the preemption
|
|
* until we exit the critical section. Otherwise, switch immediately
|
|
* to the new thread.
|
|
*/
|
|
ctd = curthread;
|
|
if (ctd->td_kse == NULL || ctd->td_kse->ke_thread != ctd)
|
|
return (0);
|
|
pri = td->td_priority;
|
|
cpri = ctd->td_priority;
|
|
if (pri >= cpri || cold /* || dumping */ || TD_IS_INHIBITED(ctd) ||
|
|
td->td_kse->ke_state != KES_THREAD)
|
|
return (0);
|
|
#ifndef FULL_PREEMPTION
|
|
if (!(pri >= PRI_MIN_ITHD && pri <= PRI_MAX_ITHD) &&
|
|
!(cpri >= PRI_MIN_IDLE))
|
|
return (0);
|
|
#endif
|
|
if (ctd->td_critnest > 1) {
|
|
CTR1(KTR_PROC, "maybe_preempt: in critical section %d",
|
|
ctd->td_critnest);
|
|
ctd->td_pflags |= TDP_OWEPREEMPT;
|
|
return (0);
|
|
}
|
|
|
|
/*
|
|
* Our thread state says that we are already on a run queue, so
|
|
* update our state as if we had been dequeued by choosethread().
|
|
*/
|
|
MPASS(TD_ON_RUNQ(td));
|
|
TD_SET_RUNNING(td);
|
|
CTR3(KTR_PROC, "preempting to thread %p (pid %d, %s)\n", td,
|
|
td->td_proc->p_pid, td->td_proc->p_comm);
|
|
mi_switch(SW_INVOL, td);
|
|
return (1);
|
|
#else
|
|
return (0);
|
|
#endif
|
|
}
|
|
|
|
#if 0
|
|
#ifndef PREEMPTION
|
|
/* XXX: There should be a non-static version of this. */
|
|
static void
|
|
printf_caddr_t(void *data)
|
|
{
|
|
printf("%s", (char *)data);
|
|
}
|
|
static char preempt_warning[] =
|
|
"WARNING: Kernel preemption is disabled, expect reduced performance.\n";
|
|
SYSINIT(preempt_warning, SI_SUB_COPYRIGHT, SI_ORDER_ANY, printf_caddr_t,
|
|
preempt_warning)
|
|
#endif
|
|
#endif
|
|
|
|
/************************************************************************
|
|
* SYSTEM RUN QUEUE manipulations and tests *
|
|
************************************************************************/
|
|
/*
|
|
* Initialize a run structure.
|
|
*/
|
|
void
|
|
runq_init(struct runq *rq)
|
|
{
|
|
int i;
|
|
|
|
bzero(rq, sizeof *rq);
|
|
for (i = 0; i < RQ_NQS; i++)
|
|
TAILQ_INIT(&rq->rq_queues[i]);
|
|
}
|
|
|
|
/*
|
|
* Clear the status bit of the queue corresponding to priority level pri,
|
|
* indicating that it is empty.
|
|
*/
|
|
static __inline void
|
|
runq_clrbit(struct runq *rq, int pri)
|
|
{
|
|
struct rqbits *rqb;
|
|
|
|
rqb = &rq->rq_status;
|
|
CTR4(KTR_RUNQ, "runq_clrbit: bits=%#x %#x bit=%#x word=%d",
|
|
rqb->rqb_bits[RQB_WORD(pri)],
|
|
rqb->rqb_bits[RQB_WORD(pri)] & ~RQB_BIT(pri),
|
|
RQB_BIT(pri), RQB_WORD(pri));
|
|
rqb->rqb_bits[RQB_WORD(pri)] &= ~RQB_BIT(pri);
|
|
}
|
|
|
|
/*
|
|
* Find the index of the first non-empty run queue. This is done by
|
|
* scanning the status bits, a set bit indicates a non-empty queue.
|
|
*/
|
|
static __inline int
|
|
runq_findbit(struct runq *rq)
|
|
{
|
|
struct rqbits *rqb;
|
|
int pri;
|
|
int i;
|
|
|
|
rqb = &rq->rq_status;
|
|
for (i = 0; i < RQB_LEN; i++)
|
|
if (rqb->rqb_bits[i]) {
|
|
pri = RQB_FFS(rqb->rqb_bits[i]) + (i << RQB_L2BPW);
|
|
CTR3(KTR_RUNQ, "runq_findbit: bits=%#x i=%d pri=%d",
|
|
rqb->rqb_bits[i], i, pri);
|
|
return (pri);
|
|
}
|
|
|
|
return (-1);
|
|
}
|
|
|
|
/*
|
|
* Set the status bit of the queue corresponding to priority level pri,
|
|
* indicating that it is non-empty.
|
|
*/
|
|
static __inline void
|
|
runq_setbit(struct runq *rq, int pri)
|
|
{
|
|
struct rqbits *rqb;
|
|
|
|
rqb = &rq->rq_status;
|
|
CTR4(KTR_RUNQ, "runq_setbit: bits=%#x %#x bit=%#x word=%d",
|
|
rqb->rqb_bits[RQB_WORD(pri)],
|
|
rqb->rqb_bits[RQB_WORD(pri)] | RQB_BIT(pri),
|
|
RQB_BIT(pri), RQB_WORD(pri));
|
|
rqb->rqb_bits[RQB_WORD(pri)] |= RQB_BIT(pri);
|
|
}
|
|
|
|
/*
|
|
* Add the KSE to the queue specified by its priority, and set the
|
|
* corresponding status bit.
|
|
*/
|
|
void
|
|
runq_add(struct runq *rq, struct kse *ke)
|
|
{
|
|
struct rqhead *rqh;
|
|
int pri;
|
|
|
|
pri = ke->ke_thread->td_priority / RQ_PPQ;
|
|
ke->ke_rqindex = pri;
|
|
runq_setbit(rq, pri);
|
|
rqh = &rq->rq_queues[pri];
|
|
CTR5(KTR_RUNQ, "runq_add: td=%p ke=%p pri=%d %d rqh=%p",
|
|
ke->ke_thread, ke, ke->ke_thread->td_priority, pri, rqh);
|
|
TAILQ_INSERT_TAIL(rqh, ke, ke_procq);
|
|
}
|
|
|
|
/*
|
|
* Return true if there are runnable processes of any priority on the run
|
|
* queue, false otherwise. Has no side effects, does not modify the run
|
|
* queue structure.
|
|
*/
|
|
int
|
|
runq_check(struct runq *rq)
|
|
{
|
|
struct rqbits *rqb;
|
|
int i;
|
|
|
|
rqb = &rq->rq_status;
|
|
for (i = 0; i < RQB_LEN; i++)
|
|
if (rqb->rqb_bits[i]) {
|
|
CTR2(KTR_RUNQ, "runq_check: bits=%#x i=%d",
|
|
rqb->rqb_bits[i], i);
|
|
return (1);
|
|
}
|
|
CTR0(KTR_RUNQ, "runq_check: empty");
|
|
|
|
return (0);
|
|
}
|
|
|
|
#if defined(SMP) && defined(SCHED_4BSD)
|
|
int runq_fuzz = 1;
|
|
SYSCTL_DECL(_kern_sched);
|
|
SYSCTL_INT(_kern_sched, OID_AUTO, runq_fuzz, CTLFLAG_RW, &runq_fuzz, 0, "");
|
|
#endif
|
|
|
|
/*
|
|
* Find the highest priority process on the run queue.
|
|
*/
|
|
struct kse *
|
|
runq_choose(struct runq *rq)
|
|
{
|
|
struct rqhead *rqh;
|
|
struct kse *ke;
|
|
int pri;
|
|
|
|
mtx_assert(&sched_lock, MA_OWNED);
|
|
while ((pri = runq_findbit(rq)) != -1) {
|
|
rqh = &rq->rq_queues[pri];
|
|
#if defined(SMP) && defined(SCHED_4BSD)
|
|
/* fuzz == 1 is normal.. 0 or less are ignored */
|
|
if (runq_fuzz > 1) {
|
|
/*
|
|
* In the first couple of entries, check if
|
|
* there is one for our CPU as a preference.
|
|
*/
|
|
int count = runq_fuzz;
|
|
int cpu = PCPU_GET(cpuid);
|
|
struct kse *ke2;
|
|
ke2 = ke = TAILQ_FIRST(rqh);
|
|
|
|
while (count-- && ke2) {
|
|
if (ke->ke_thread->td_lastcpu == cpu) {
|
|
ke = ke2;
|
|
break;
|
|
}
|
|
ke2 = TAILQ_NEXT(ke2, ke_procq);
|
|
}
|
|
} else
|
|
#endif
|
|
ke = TAILQ_FIRST(rqh);
|
|
KASSERT(ke != NULL, ("runq_choose: no proc on busy queue"));
|
|
CTR3(KTR_RUNQ,
|
|
"runq_choose: pri=%d kse=%p rqh=%p", pri, ke, rqh);
|
|
return (ke);
|
|
}
|
|
CTR1(KTR_RUNQ, "runq_choose: idleproc pri=%d", pri);
|
|
|
|
return (NULL);
|
|
}
|
|
|
|
/*
|
|
* Remove the KSE from the queue specified by its priority, and clear the
|
|
* corresponding status bit if the queue becomes empty.
|
|
* Caller must set ke->ke_state afterwards.
|
|
*/
|
|
void
|
|
runq_remove(struct runq *rq, struct kse *ke)
|
|
{
|
|
struct rqhead *rqh;
|
|
int pri;
|
|
|
|
KASSERT(ke->ke_proc->p_sflag & PS_INMEM,
|
|
("runq_remove: process swapped out"));
|
|
pri = ke->ke_rqindex;
|
|
rqh = &rq->rq_queues[pri];
|
|
CTR5(KTR_RUNQ, "runq_remove: td=%p, ke=%p pri=%d %d rqh=%p",
|
|
ke->ke_thread, ke, ke->ke_thread->td_priority, pri, rqh);
|
|
KASSERT(ke != NULL, ("runq_remove: no proc on busy queue"));
|
|
TAILQ_REMOVE(rqh, ke, ke_procq);
|
|
if (TAILQ_EMPTY(rqh)) {
|
|
CTR0(KTR_RUNQ, "runq_remove: empty");
|
|
runq_clrbit(rq, pri);
|
|
}
|
|
}
|
|
|